Can a Lennox furnace last 30 years?

Can a Lennox furnace last 30 years is possible for very old heavy-duty models but rare and not expected for modern Lennox furnaces, as average life of Lennox furnace is 18 to 22 years and maximum with excellent care is 25 to 28 years. Old Lennox furnaces from 1970s and early 1980s like Lennox G8 and G12 built with heavy heat exchangers and simple controls could last 30 to 35 years if heat exchanger did not crack and parts replaced, and some still operating today at 35 years with heavy maintenance. Modern Lennox furnaces from 1990s onward like ML296V, EL296V, and SLP99V use thinner aluminized steel or stainless steel heat exchangers, more electronics, and variable speed motors that typically fail after 15 to 22 years, with heat exchangers developing cracks after 20 years due to thermal stress, and control boards failing after 12 to 15 years. Factors that could allow Lennox furnace to reach 30 years include running only 3 to 4 months per year in mild climate, annual maintenance with filter changed every 2 months, low usage, and replacing major parts like blower motor twice at 400 to 700 dollars each, gas valve, igniter multiple times at 100 to 200 dollars, and control board. However, after 20 years, furnace efficiency at 80 percent versus modern 96 to 99 percent causes higher gas bills, parts become obsolete, and safety risk from cracked heat exchanger that can leak carbon monoxide increases significantly. Most pros recommend replacing after 20 years for safety.